1. Field of the Invention
The present invention relates to a lithium oxide cathode active material for use in a lithium secondary battery and a lithium secondary battery using the cathode active material, and more particularly, to a lithium oxide cathode active material that has particular relative peak intensities in its Raman spectrum and a lithium secondary battery using the same.
2. Description of the Related Art
With the recent rapid advancements in the manufacturing of portable, cordless appliances, lithium secondary batteries have become viable power sources for smaller electronic devices, such as laptop computers, mobile phones, camcorders, and the like. Since lithium cobalt oxide (LiCoO2) was found to be an effective cathode active material, intensive research has been conducted into lithium complex oxides.
Regarding the development of secondary batteries, the cycle life, charging/discharging characteristic, and capacity characteristic are considered important performance measures. The composition and structure of cathode and anode active materials, an electrolyte, a binder, and the like, which constitute a secondary battery, are the main factors that affect the characteristics of the secondary battery.
A battery having desired characteristics may be manufactured by evaluating the factors that affect the performance of batteries. As disclosed in U.S. Pat. Nos. 5,344,726, 6,335,121, and the like, methods of evaluating the characteristics of batteries that depend on anode active materials in the manufacture of batteries include an X-ray technique and Raman spectroscopy by which peaks of carbonaceous anode active materials are read.
However, methods of evaluating characteristics of batteries that depend on cathode active materials based on Raman spectroscopy have been scarcely reported because a cathode active material is used generally as a mixture with a binder, a conductive carbon, and the like, in manufacturing a cathode and is difficult to be isolated from the other materials for analysis.
Therefore, conventionally, performance evaluation, for example, on the cycle life, charging/discharging characteristic, and capacity characteristic, has been carried out directly using complete batteries, not using cathode active materials. Obviously, X-ray diffraction analysis is often used to predict a cell performance in the step of developing active materials. However, a minor structural change of cathode active materials cannot be observed with this analysis method. There is no alternative but to evaluate the life span and safety measures using a complete battery when a particular cathode active material is used in the battery, thus increasing manufacturing time and costs in the development of cathode active materials batteries.